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An interesting solution for NASCAR race engine alternators

News International-French

23 Feb 2011

With all the jostling and bumping going on, it is sometimes easy to forget that stock car racing is after all an endurance event. Top NASCAR teams work to ensure reliability for every race on every component. Each part is designed to ensure that 700 or 800 kilometres are clocked up without incident. If any component becomes a problem or appears to be a liability, the challenge must be met with swift and decisive action. Here is an innovative solution for alternators.

Alternators are one of the most problem-prone parts on NASCAR race engines. The combination of high under-hood temperatures (up to 180°C), high vibration (up to 600 g), and high electrical current demand (up to 140 A) presents unprecedented design challenges. In mid-2009, NASCAR approved routing a maximum 25.4-mm duct from the side of the radiator shroud to the alternator. Initial attempts at implementing the duct involved fitting a secondary rear cover to the alternator with an integral hose attachment. Packaging was tight and the cooling efficiency of the cover was sacrificed by retaining the original OEM rear cover.


Withstanding severe environments

A meeting with CRP at the first MotorsportExpotech show in 2008 in Italy gave Dr. Andrew Randolph, Engine Technical Director for Earnhardt Childress Racing (ECR), another option for this type of challenge. ECR designed a replacement rear cover for a standard NASCAR Bosch alternator that packaged well and provided maximum cooling efficiency. Once this potential solution was found, the next step involved deciding how to manufacture the parts using a reliable material and a fast method. Traditional machining and moulding offer reliable materials, but included the cost of tooling and the penalty of time. A call was made to CRP Technology and after further discussions, work began with the CRP USA team on options for the part that needed to be made.


Windform XT – the carbon-fibre-reinforced polyamide for selective laser sintering (SLS) developed by CRP Technology – would normally have been a clear choice, but in this case the added challenge of the current passing through the live contact post represented an obstacle for the partially conductive material. The compact design gave little room for creating isolation, which meant that Windform XT with its carbon fibre content was not the correct fit. Into the spotlight stepped the newly developed Windform LX material, a glass-fibre-reinforced polyamide using SLS too. Windform LX was given a thorough vetting as the possible candidate and had the correct combination of strength and thermal resistance for ECR’s solution.


Six alternator cooling covers were produced and subjected to initial testing. Subsequent track testing with temperature stickers showed an 11°C reduction in maximum stator temperature with the new cover attached. Cover durability in the challenging under-hood environment was excellent. The next step was to outfit the race teams with this new component. The move from rapid prototype to rapid production proved very simple, as the Windform LX material was suited to resist the race conditions. A production run of 50 parts was ordered and then installed on the race engines.


As the season drew to a close twelve races later, the success of the part had become as common place as finishing an 800-km race. Randolph states “Windform LX alternator covers from CRP fit perfectly from the onset and we have not had a single alternator failure since installing them on all ECR NASCAR Cup engines.”


Windform LX combined with the design and engineering experience of the ECR team proved that a solution did not have to be limited to a test run on the Dyno. The depth of the Windform material line and CRP USA once again proved that their work is not only track tested, but also race proven.